Apparatus for expanding finely divided particles of obsidian-like material



Oct. 22, 1957 E. B. WHITE 2,810,810

APPARATUS FOR EXPANDING FINELY DIVIDED PARTICLES OF OBSIDIAN-LIKEMATERIAL Filed March 28, 1949 2 Sheets-Sheet 1 Blower Mechanism Oct. 22,1957 E. 8. WHITE 2,810,810

APPARATUS FOR EXPANDING FINELY DIVIDED PARTICLES OF OBSIDIAN-LIKEMATERIAL Filed March 28, 1949 2 Sheets-Sheet 2 United States PatentAPPARATUS FOR EXPANDING FINELY DIVIDED PARTICLES 0F OBSIDIAN-LIKEMATERIAL Eugene B. White, Oak Park, Ill.

Application March 28, 1949, Serial No. 83,822

1 Claim. (Cl. 219--10.65)

The invention relates generally to the production of silicious materialin spherical microscopic form, and more particularly to an improvedprocess and apparatus for producing the same. The invention isparticularly adapted, for example, to the production of filtermaterials, such as that disclosed in my copending application, SerialNo. 43,991, filed August 13, 1948, and titled Filter and Ma terialTherefor, now abandoned.

Filter material of this type comprises extremely fine particles of asuitable obsidianite, such as perlite, which has been expanded by theapplication of heat thereto to form a porous structure.

The present invention is, therefore, particularly adapted for theproduction of microscopic particles of expanded material which, forexample, may range in size from about it) to 256 or more microns ascompared to previous methods and apparatus for expanding similarmaterials which have involved considerably greater sized pieces of suchmaterial.

In the past, the accepted practice in expanding fusible material, suchas here involved, has broadly consisted of mixing the material to betreated with air and a suitable fuel, passing the mixture into asuitable chamber in which the fuel is ignited, whereby the heat ofcombustion thereof is sufficiently high to cause fusing of the material,and as the latter contains a percentage of moisture, it results in theexpansion thereof. An example of apparatus for accomplishing theseresults is illustrated in Patent 2,044,680, issued on June 16, 1936, toC. G. Gilbert. As set forth in such patent, considerable difficulty hasbeen experienced in obtaining uniform results, as well as the inabilityto accurately control the variables inherent in such process. Obviously,in any process employing heat of combustion as the expanding medium, aserious problem with respect to the extinguishment of combustion due toabsorption of heat by the particles being expanded, and as pointed outin the patent above referred to, the heat absorption rate of theparticle increases tremendously as the particle size dimishes, and thatalong with the increased absorption rate resulting from decreasing ofparticle size, the rate of absorption increases directly with theincrease in the total amount of solids present at the combustion point.Consequently, in any process embodying a mixture of the particles to beexpanded with the combustible material, the quantity of expandedmaterial produced is definitely limited, as the dispersion of theparticles must be limited to a point at which the rate of heatabsorption is below the rate of combustion, whereby reignition of thegases enveloping the particles will take place. The Gilbert patentattempts to partially correct the difiiculty by controllably dispersingthe individual particles of the material to be treated, employing,however, temperatures of combustion as the temperatures of expansion.

The present invention is directed to a process whereby heat is appliedto the particles to be expanded without combining the same withcombustible fuel as, for example, utilizing radiated heat created byhigh frequency induction, whereby all variables involved in theexpansion of the material may be readily and accurately controlled, andby means of which the characteristics of the expanded material as torange of size, density, tensile strength, etc., may be produced, asdesired, in the finished material.

The present invention is, therefore, directed to a novel process forexpanding particles of fusible material of microscopic size, whichprocess is extremely efficient, and by means of which accurate controlof the finished product may be maintained.

A further object of the invention is the utilization of such a processcapable of producing high uniformity of the finished material and thedesired uniform expansion of all the material treated without requiringreprocessing.

Another object of the invention is the provision of such a process whichmay be readily practiced on a commercial basis whereby the expandedmaterial may be produced at relatively low cost.

A further object of the invention is the production of novel apparatuswhich is exceedingly simple in construction and efficient in operationfor expanding microscopic particles of fusible material.

A further object of the invention is the provision of a novel method andapparatus for performing the same by means of which expanded particlesof microscopic size may be produced and collected without the necessityof employing classifiers, or the like.

Many other objects and advantages of the construction herein shown anddescribed will be obvious to those skilled in the art from thedisclosure herein given.

In practicing the present invention, the material to be expanded isfirst pulverized to a pre-determined size dependent upon thecharacteristics desired in the finished material, following which thepulverized material is controllably dispersed in a suitable vehicle,such as air or a suitable gas, the latter or air, if desired, beingpre-heated. The air and suspended material is then passed through achamber heated by radiation, whereby all particles of the dispersion areuniformly heated to the desired temperature, resulting in expansion ofthe material, which is then permitted to cool below the fusingtemperature, and subsequently collected. The expanding chamber ispreferably heated by high frequency induction whereby the size of theexpanding zone, as well as the temperature therein, may be veryaccurately controlled. I am thus able to ac curately control thedispersion of the particles in the air or other vehicle, the temperatureof the expanding zone through which the particles pass, the rate ofpassage through the expanding zone, as well as the size or length ofsuch a zone.

In addition to the above results achieved by the use of the presentinvention, the present heating and cooling of the fusible material mayalso be readily controlled, and it will, therefore, be apparent thateach individual step in my improved process may be individuallycontrolled whereby the finished material may be produced with anydesired inherent characteristics.

For the purpose of illustration, the process will be described inconjunction with one form of apparatus for performing the same.

In the drawings, wherein like refernce characters indicate like orcorresponding parts:

Fig. l is a side elevational view of an apparatus for carrying out thepresent invention;

Fig. 2 is a side elevational view of one of the heating tubes employedwith portions thereof and the surrounding structure shown in section;

Fig. 3 is a sectional view taken approximately on the line 3-3 of Fig.4; and

Fig. 4 is a sectional view taken approximately on the line 4-4 of Fig.3.

Referring to the drawings, and more particularly to Fig. l, 1 indicatesgenerally a pulverizer comprising a pulverizing unit 2, having anopening 3 for the reception of V the crude fusible material, and anoutlet duct 4 for the pulverized material. The pulverizer 1 is adaptedto produce a pulverized fusible material the size of the individualparticles ranging from 1 to 25 microns, as desired, and units of thistype are readily procurable in commerce. Consequently the details ofconstruction thereof form no part of the present invention.

The outlet of the pulverizer 1 is connected to collector mechanismthrough a duct 6, and in the construction illustrated, includes a bagmember 7 and lower mechanism, indicated generally by the numeral 8. Thecollector mechanism 5 is operative to move the pulverized material fromthe pulverizer 1 through the duct 6 and collect such material in ahopper, the lower end of which is indicated at 11. The collectormechanism 5, including the bag 7 and blower mechanism 8, is commerciallyprocurable; consequently, the details thereof form no part of thepresent invention.

Positioned below the collector mechanism 5 is a heating or ovenstructure, indicated generally by the numeral 12, the details of whichare illustrated in Figs. 2, 3, and 4.

Referring to Figs. 2, 3, and 4, the structure 12, in the constructionillustrated, comprises a plurality of tubes 13, five tubes beingemployed in the present instance, as illustrated in Fig. 3. The tubes 13are hollow and constructed of a suitable ferromagnetic material having avery high melting point. Each tube 13 is supported at its lower end by abase member 14, and at its upper end by a member 15, the ends of thetube being inset in the respective members, as clearly illustrated inFigs. 2 and 4. The members 14 and 15 are constructed from a suitableinsulating material capable of withstanding very high temperatures, suchas a mixture of asbestos and a suitable cement, or the like, an exampleof which is known in the trade as Electrobestos. Each tube 13 forms anoven or heating chamber in which the pulverized material is adapted tobe expanded and, in the construction illustrated, each tube 13 isadapted to be heated by induction, each tube having an induction coil 16encircling a portion of the tube with the ends 17 of each coil extendingthrough a supporting member 18, the ends of which are also inset in therespective members 14 and 15. Each member 18 is constructed from asuitable insulating material which may, if desired, be the same materialas the members 14 and 15. The ends of each coil 16 are provided withsuitable connectors 19, to which are secured electrical conductors 21,the latter being adapted to be operably connected to a suitable sourceof high frequency current. The tube 13, and members 14, 15, and 18 maybe held in assembled relation by any suitable means, such as bolts 20and nuts 20'. As high temperatures of 2,000 degrees Fahrenheit or moremay be involved, each coil 16 is preferably made from hol low tubingwhereby the ends 17 of the coil may be operatively connected to acoolant supply line 22, and a return line 23 whereby each coil, whichnormally would be made of a relatively low melting point metal, may besatisfactorily cooled and thus maintained below melting temperatures.

As high frequency current is passed through the coils 16, the portionsof the tubes 13 positioned in the coil will be heated by inductionwhereby material passing through the tubes will be heated by radiationfrom the interior wall surface of the respective tubes.

As illustrated in Figs. 3 and 4, the member 15 is provided with acentral conical shaped portion 24, preferably having a face 25 of metalor other suitable material of sufficient hardness to eliminate undueabrasion of the portion 24 by action of the pulverized material as itflows through the device. Mounted on and secured to the top of themember 15 by the bolts 20 is a generally conical shaped housing 26connected at its upper end to the end 11 of the hopper 9, adjacentportions of the end 11 andmember 26 being provided with complementaryflanges 27 and 28 secured together by bolts 29, or other suitable means,with a gasket 31 being interposed between the two flanges. Surroundingthe conical portion 24 is an annular shaped channel or groove 32, whichoperatively communicates, at spaced points, with the interior of thetubes 13.

The upper end of each tube 13 is provided with a Venturi sleeve 33,which is formed with an orifice 34, the side interior walls of thesleeve tapering outwardly the orifice 34 towards the respective ends ofthe sleeve, as clearly illustrated in Fig. 4. Positioned above andaxially aligned with each of the orifices 34 are respective nozzles 35adapted to be operatively connected to an air or gas supply line,indicated generally by the numeral 36, through a suitable valve 37having a control handle or wheel 38. All of the respective valves 37 areoperatively connected to the supply line 36, the connecting pipingbetween the respective valves, however, not being shown.

Positioned below and secured to the base member 14 by the bolts 20 is asuitable housing 39 adapted to receive and collect material passingdownward from the respective tubes 13, the member 14 being provided withbores 41, each aligned with one of the respective tubes 13 to permitpassage of the material through the member and into the collectorhousing 39, the latter member provided at its lower end with a suitablevalve 42 and means for attaching a bag, or other receptacle, to thehousing as, for example, the bag B indicated in dotted lines in Fig. 1.

In the operation of the device, the fusible material is inserted in thehopper 3 and passed through the pulverizer 2, which will reduce thematerial to particles of a pre-determined size. The pulverized particlesare then moved through the duct 6 to the collector mechanism 5, wherethey are deposited in the bag 7, and ultimately dropped to the lower end11 of the hopper 9, thus passing into the housing 26, where the conicalshaped portion 24 will direct the material to the upper ends of thesleeves The valves 37 are each adjusted to admit a desired amount of airthrough the nozzles 35, and carry the pulverized material into the tubes13, Where the material will pass downwardly through the heated portionsof the tubes, and out the lower ends of the latter into the hopper 39.it will be apparent that as the particles of the material beingprocessed have a density less than one, the rate of flow of materialinto the tubes 13 is substantially dependent upon the amount of airdischarged from the nozzles 35, whereby adjustment of the valve 37 willprovide a convenient means for controlling the flow of material throughthe tube. As the tubes 13 are heated, there would be a normal tendencyfor an upward circulation of air through the tubes by convection, and insome cases it may be desirable that the amount of air admitted throughthe nozzles 35 be merely sufiicient to insure a flow of material intothe tubes 13, in which case the amount of air flow would be more or lessslightly above that required to otfset the upward convection fiow of airin the tube whereby the particles pass through the tube substantially bythe influence of gravity. The temperature of the heated portions of thetubes 13, and thus the expansion of the particles passing through thetube, may be readily and accurately controiled by varying the frequencyof the voltage applied to the coils 16, and I have found that a range offrom 100,000 to 200,000 cycles in the voltage applied to the coil 16will provide an adequate temperature range for the purposes intended.The coil 16 is preferably spaced a distance from the upper member 15 toprovide a pre-heating zone for the material being proc essed. Thus asthe material passes through the portion 13a located between the member15 and the top end of the coil 16, such material will receive an amountof pre-heating prior to passing into the hot zone encircled by the coil,such pro-heating resulting from the heating of the portion 13a byconduction to a temperature somewhat less than that in the hot zone.Likewise, the lower exposed portion 13b of each tube between the lowerend of the coil 16 and the member 14 provides a cooling zone, as thetemperature of this portion of the tube will be less than that in thehot zone, the length of the portion 13b being sufiicient to insure thetemperature reduction of the processed particles below the solidifyingpoint prior to their entry into the hopper 39.

It will be noted from the above description that the apparatus abovedescribed provides accurate control of the flow of the material throughthe tubes 13, and also the accurate control of the temperature at whichthe particles are heated; also the range of particle sizes of theunprocessed material may be controlled by suitable adjustment of thepulverizer 2. The construction described also creates a substantiallyuniform dispersion of the particles passing through the respectivetubes, and as the particles are heated by radiation, it will be apparentthat substantially uniform heating of the particles dispersed in thetube is achieved regardless of the particular concentration of theparticles. As a result, the fusing together of individual particles iseliminated. Likewise, as no reactions of combustion in the tubes areinvolved, a uniform and complete processing of the material is achieved,and it is, therefore, unnecessary to reprocess any of the material onceit has passed through the tubes.

In view of the accurate control of the variables involved, I am able, inpracticing my invention, to produce not only uniform and completeresults, but am also able to accurately control both the size andstructure of the expanded particles. For example, by proper control ofthe flow of and temperature at which the material is heated, theparticle may be substantially completely expanded whereby it Will have arelatively thin and fragile cellular structure or, if desired, theparticle may be only partially expanded, resulting in a smaller particlehaving a thicker and stronger cellular structure.

While I have illustrated the application of my novel process by means ofthe apparatus herein described, it will be apparent that the presentprocess is applicable to and may be carried out by means of varioustypes of apparatus, which may employ other means of heating theparticles to expansion temperature, as well as other means forcontrolling the dispersion of material prior to the applicatiin of heatthereto. Likewise, While I have referred to the injection or dispersionof material by means of air, obviously, if desired, a suitable gas maybe employed and, in either case, the gas or air may, if desired, bepreheated prior to the dispersion of the material therein. It will benoted from the above description that the present invention permits theproduction of an expanded fusible material, the size and characteristicsof which may be accurately controlled to produce a particle ofmicroscopic size which is highly vesicular and substantially sphericalin shape; likewise, that the process herein de scribed may be performedby substantially relatively simple apparatus, such as the example hereinshown and described.

Having thus described my invention, it is obvious that variousimmaterial modifications may be made in the same without departing fromthe spirit of my invention; hence, I do not wish to be understood aslimiting myself to the exact form, construction, arrangement, andcombination of parts herein shown and described or uses mentioned.

What I claim as new and desire to secure by Letters Patent is:

Apparatus for expanding finely divided particles of obsidian-likematerial from a predetermined particle size varying within the range offrom substantially 1 to 25 microns comprising top and bottom supportingmembers, a tube extending between said members, said tube being open atboth ends, a container for the material positioned above andcommunicating with the upper end of said tube, such tube end beingformed with a Venturi passage therein, a gas discharge nozzle positionedadjacent the upper end of each tube for directing a gas into saidpassage, said nozzle being adapted to be operatively connected to asource of gas under pressure, means for controlling the flow of gas fromsaid nozzle for dispersing the finely divided particles in the gasforming a substantially uniform suspended mass, an induction coilsurrounding a portion of said tube, such portion having side walls of aterm-magnetic material, said coil being adapted to be connected to asource of high frequency current for heating the suspended mass abovethe fusing temperature of said material whereby microscopic particles ofexpanded material are formed varying within the range of fromsubstantially 10 to 250 microns in particle size, said tube extendingbelow said coil a predetermined distance to provide a cooling space formaterial passing therethrough, and means adjacent the opposite end ofsaid tube for collecting the treated material.

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